Terminal bushing



Dec. 2, 1947. l.. MAUERER TERMINAL BUSING Filed May 24, 1944 @Wmfwm Patented Dec. 2, 1947 TERMINAL BUSHING Leopold Mauerer, Chicago, Ill., assignor to J elferson Electric Company, Bellwood, Ill., a corporation of Illinois Application May 24, 1944, Serial No. 537,050

2 Claims.

This invention relates to an improved terminal bushing for casings for transformers and other electrical apparatus, and in particular to an improved construction which provides an air-tight seal between the casing, the conductor and the bushing proper.

The usual type of bushing for small transformers and the like comprises a body of insulating material disposed in or adjacent an aperture in the casing, and which serves to space a conductor passing through the bushing from the edges of the apertured casing. Various expedients are used to provide an air-tight construction between the insulating body and the metal casing. The screw threaded clamping means frequently used on large transformer bushings is not practicable for considerations of space in small radio transformers and the like. Other expedients involve the use of a shaped member of U or S-shaped cross-section which clamps both the insulating body and the edge of the transformer casing to provide an air-tight construction. This expedient, however, is not entirely satisfactory for the reason that the ringshaped member is exposed and is subject to blows or other forces which might dent or otherwise deform it in a manner to break the seal.

This invention contemplates the use of a ringshaped member which is associated with the insulating body in a non-exposed and protected manner, and which, being spun over the edge of the apertured casing, cannot be bent or deformed so as to break the seal by any exterior force, except as such force may be great enough to dam- A age the insulating body as well.

It is an object of this invention to provide a terminal bushing which is secured to the casing of a transformer or the like by a skirt which is partially embedded in the insulating body of the bushing.

It is a further object of this invention to provide a transformer bushing having a body member of relatively shockproof plastic material in combination with a skirt in the form of a molded insert depending from the casing contacting surface of said body member, so that the bushing may be secured to the casing in an air-tight manner.

It is another object of this invention to provide in a terminal bushing which is adapted to overlie an aperture in a transformer casing or the like, a barrier to the passage of air along the contacting flat surfaces, this barrier being in the form of a cylindrical member secured at either end to the body of the bushing and to the transformer casing, and which surrounds the conductor leading up to a terminal in the bushing.

It is a still further object to provide a terminal bushing for cooperation with an apertured transformer casing or the like which includes a terminal to which a conductor may be secured in air-tight relationship, and which bushing is otherwise secured in an air-tight relationship to the transformer casing.

Other objects, features and advantages will appear as this description proceeds.

With reference now to the drawings which form a part of this description and in which like reference numerals designate like parts:

Fig. 1 is a view of a small transformer embodying a preferred form of this invention;

Fig. 2 is an enlarged plan view of a terminal bushing shown in Fig. 1;

Fig. 3 is a sectional elevation of the transformer bushing shown in Fig. 2;

Fig, 4 is a phantom elevation of the bushing shown in Fig. 3;

Fig. 5 is a section of a modified form of this invention; and

Fig. 6 is a section of a further modification.

With reference now to Figs. 1 to 4, the reference numeral I0 designates generally a transformer which includes a cover II, or other portion of the transformer casing, and a plurality of terminal bushings I2.

Each terminal bushing comprises a body member I3, as shown in Fig. 3, which is preferably formed of a plastic having a relatively high impact test. It has been found that a phenolic molding material which is mineral lled and has high heat resistance and high impact strength is particularly well adapted for the terminal bushing herein shown and described. The body member is molded with two inserts, a central tubular insert I4, and a cylindrical skirt I1. The lower surface of the body member may be recessed centrally of the skirt I1 and the lower end of the tubular insert I4 is flush with the recessed surface. The upper end thereof is extended beyond the upper surface of the body member I3. The tubular insert is provided with an annular crimp or ridge I5 which is milled as indicated at I6 in Fig, 4, this configuration serving to anchor it in the plastic body member against both longitudinal and rotational displacement.

The insert which comprises the cylindrical skirt i1 is molded in the body member so that the lower end thereof extends beyond the bottom surface of the body member. The upper end of the insert comprises an expanded edge IS which is provided with milling I9 so as to prevent longitudinal and rotational displacement.

In assembling the bushing, an L-shaped terminal 23, the lower end of which is apertured, is placed over the extended end of the tubular insert, i4, and this extended end is spun over the terminal 23 as indicated by the reference numeral 2E. The L-shaped terminal may be provided with burrs 2d which bite into the body member of the bushing to prevent rotation.

The bushing is now seated over the circular aperture formed in the cover I I. The edge of the aperture is designated by the reference numeral 21, and after the skirt I1 is fitted into the apertured casing the lower end thereof is spun over the edge 21 as indicated by the reference numeral 28. The joint between the skirt and the casing may be filled with a bead of solder 29, The solder provides an air-tight connection.

Then a conductor 2D, the end of which has been bared of its insulation 2I, is brought up through a circular aperture in the transformer cover Il, and is inserted into the central tubular insert I4, and the space between the two is filled with solder 22. rIhis not only proves a good electrical connection but also joint.

The cover il is then replaced on the transformer and a conductor to an external circuit may be soldered to the terminal 23. The latter is provided with an aperture 26 through which said external conductor to an exterior circuit may be threaded prior to soldering.

It will be observed from a consideration of Fig. 3 that any tendency of air to creep between the contacting surfaces of the b-ushing and of the casing is prevented by the skirt l1 which provides an impenetrable barrier. The fact that tis skirt is a molded insert prevents any leakage of air upwardly and around its surface due to the intimate nature of the contacting surfaces. The bead of solder 29 prevents any leakage of air downwardly around the skirt. Similarly, the solder 22 prevents any leakage of air through the central tubular insert.

If preferred, a gasket may be disposed between the plastic body member I3 and the cover II, instead of providing the bead of solder 29, such as shown in Fig. 6, or both may be used. However, a solder seal is preferred from the viewpoint of ease of manufacture.

Inasmuch as the cylindrical skirt l1 is wholly enclosed, it cannot be bent 0r otherwise damaged by a blow. Furthermore, the use of a high impact plastic will serve to protect the skirt I 1 from the effect of blows on the body portion I3- A modified form of this invention is shown in Fig. 5, this modification being Substantially identical to that shown in Figs. 2 to 4, with the exception that the central portion 30. of the body member I3 projects downwardly. The Fig, 5 bushing comprises a body member I3. having a skirt I1 molded into the lower surface thereof.

insures an air-tight.

4 The central tubular insert I4' is longer than the insert I4 of Fig. 3; the insert I4' extends all the way through the body member I3 and the projecting central portion 3U.

A further modification, adapted for somewhat larger installations, is shown in Fig. 6 and comprises a molded plastic body member 3| having a central insert 32 provided with exterior and internal termninals 33 and 34 respectively. An enlarged intermediate portion 35 is provided with a coarse knurl 36 so that the insert 32 may be securely embedded in the body portion 3I. The central insert 32 is considerably larger than the body portion, and the downwardly extended portion 31 of the insert is embedded in a sleeve 3B which is integral with and extends downwardly from the body portion 3 I.

A second insert 39, in the form of a cylindrical skirt, projects from the lower surface of the body portion 3|. This is substantially the same as the skirt I1 of Figs. 3 and 4, and is embedded in the plastic body member in the same way as described above.

The bushing is assembled t0 the cover II in much the same way as the bushing of Figs. 2 to 4, except that Fig. 6 shows, by way of variation, the use of a gasket 40 between the bushing and the cover to provide an air-tight seal, instead of a bead of solder around the spun over edge of the skirt.

The internal terminal 34 then is provided with a shallow bore and cut away edges so as to form a tubular extension 4I which is spun over a terminal clip 42 to which an internal conductor can be soldered.

An external conductor can be soldered to the external terminal 33.

Although only preferred embodiments of this invention have been shown and described herein, it will be understood that various modifications and changes therein may be made without departing from the spirit of this invention, The drawings and the foregoing description are deemed to be illustrative only and this invention is to be limited only by the appended claims.

I claim:

1.' A terminal bushing comprising a plastic body member having a central tubular insert projecting from the upper surface thereof and extending all the way through said body member and a. tubular insert concentrically disposed with respect to said first mentioned insert, and projecting from the bottom surface of said body member, said central tubular insert being adapted to receive a conductor, and said second mentioned insert being deformable for engagement with the edge of an apertured transformer casing or the like, and an apertured terminal member fitting over the projecting portion of said first mentioned tubular insert, and provided with burrs which bite into said upper surface, said first mentioned tubular insert being spun over into engagement with said terminal member.

2. A terminal bushing comprising a plastic body member having a central tubular insert projecting from the upper' surface thereof and extending all the way through said body member and a tubular insert concentrically disposed with respect to said first mentioned insert, and projecting from the bottoni surface of said body member, said central tubular insert being adapted to receive a conductor, and said second mentioned insert being deformable for engagement with the edge of an apertured transformer casing or the like, and an apertured terminal member fitting over the pro- 5 6 jectng portion of said rst mentioned tubular Number Name Date insert, said rst mentioned tubular insert being 2,307,561 Bailey Jan. 5, 1943 spun over into engagement with said terminal 2,299,750 Hull et a1 Oct. 27, 1942 member. 1,759,997 Pieper May 27, 1930 LEOPOLD MAUERER. 5 2,174,374 Beggs Sept. 26, 1939 2,355,864 Hartzell Aug. 15, 1944 REFERENCES CITED 1,963,228 DaCosta June 19, 1934 The following references are of record in the FOREIGN PATENTS me of mls patent' 10 Number Country Date UNITED STATES PATENTS 509,169 Great Britain July 12, 1939 284,897 Great Britain Feb. 9, 1928 Number Name Date 385,068 Greatv Britain Dec. 22, 1932 1,699,744 Marbury Jan. 22, 1929 26,077 Great Britain 1910 

